The siliceous residue in cement
I have a problem which i can't understand, someone can help me.
My plan is producing Type 1 - C150 cement and the aggregate gradation dose not have puzzolan. Thus, cement product can't contain high siliceous residue but in fact the siliceous residue is rather high compare with RD (RD: siliceous residue =0.1%->0.5%; the plan's siliceous residue = 0.84%), i really don't know that where is the siliceous residue come from?
Some one explain this problem 4 me and tell me how can i solve it .
Thanks & regard
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Re: The siliceous residue in cement
A common source of insoluble residue in cement is unreacted silica, due to coarse silica in the raw meal.
If there is a sufficient quantity of very coarse quartz crystals (>90um), these will not be small enough to completely react with CaO to form C2S and will remain in the clinker as relict quartz in the centre of large dense C2S clusters. This unreacted quartz will increase the insoluble residue proportionately. Clinker microscopy can normaly identify such a situation.
If this is the case, the solution is to grind your raw meal finer... or separately grind the raw material responsible for the coarse quartz content. eg sand.